I am not sure about the triac either other than it varies the wattage for one of the heaters. The other is controlled by the heater relay on the board. So I assume if the triac were bad you would still get heat from the other heater.

Can you tell if the blower is actually running or not?

I think it is either in the blower motor or the inverter. As I said before, the inverter is the only thing that will cause all three error-codes but I canít say for sure if it is your problem or not. I have been through this before and have seen the motor check ok ohms wise so I change the inverter then still end up having to replace the motor to get it going. I have called GE technical assistance for this reason and all they tell me is to replace both, which is not helpful at all.